How to programatically compare an entire row in R?

Question

I have the following dataframe in R:
data= Time X1 X2 X3 1 1 0 0 2 1 1 1 3 0 0 1 4 1 1 1 5 0 0 0 6 0 1 1 7 1 1 1 8 0 0

Answer 1

Here's a couple of options using a merge:

merge(list(X1=0,X2=1,X3=1), dat)
#or
merge(setNames(list(0,1,1),c("X1","X2","X3")), dat)

Or even using positional indexes based on what columns you want matched up:

L <- list(0,1,1)
merge(L, dat, by.x=seq_along(L), by.y=2:4)

All of which return:

#  X1 X2 X3 Time
#1  0  1  1    6

If your matching variables are all of the same type, you could also safely do it via matrix comparison like:

dat[colSums(t(dat[c("X1","X2","X3")]) == c(0,1,1)) == 3,]